Atrial fibrillation (AF) is the most frequent arrhythmia encountered in clinical practice and is the most common arrhythmia necessitating hospital admission. Nearly three million people in the U.S. have Atrial Fibrillation. Americans over 40 have a one in four lifetime risk of developing Atrial Fibrillation. Currently there is only one practical treatment, pulmonary vein isolation (PVI) with a radiofrequency (RF) ablation catheter. Of the 3 million people suffering from Atrial Fibrillation, only about 3,000 (0.1%) annually are treated and cured with this complex and risky procedure. RF ablation creates hyperthermia lesions and inevitably involves some degree of tissue disruption that increases the risk for perforation and stroke. In contrast, the destruction of tissue by freezing results in minimal tissue disruption and preserves basic underlying tissue architecture. Treatment using cryoablation is attractive because of its inherent safety, however the promise of cryoablation via catheterization has not yet been fully realized because of technical shortcomings. Currently used cardiac cryoablation catheters suffer from lack of cooling power. The bottleneck is in the amount of vapor that can be exhausted through the narrow catheter (like breathing through a straw). As a result, the success of cryoablation is reduced and, by necessity, radio frequency ablation has remained the treatment of choice despite its shortcomings. We propose a method to dramatically increase the cooling power of cardiac cryoablation catheters by eliminating the need to exhaust the vapor. Instead, the vapor will be re-circulated in a closed cycle miniature cryo refrigeration system. Our goal is to compress, condense and re-use the vapor inside the catheter. Advanced Refrigeration Technologies (ART) proposes to achieve these aims with two innovative technologies: 1) ART's laser-powered compressor technology and 2) ART's microchannel heat exchanger technology. The resulting liquefier (compressor+condenser) will eliminate the need to exhaust the vapor all together. During Phase I the following three specific aims will be addressed: 1. Feasibility of our laser-powered compressor technology to pressurize vapor to liquefaction pressure. 2. Feasibility of our heat exchanger technology to effectively cool, condensate and liquefy the vapor. 3. Demonstration of cryoablation on live heart tissue. In subsequent work, the device will be implanted in a cardiac cryoablation balloon catheter. Stronger cryo will impact public health by providing to the mainstream electrocardiologists a safe tool to treat the general public. PUBLIC HEALTH RELEVANCE: Three million people in the U.S. suffer from Atrial Fibrillation. Americans over 40 years old have a one in four risk of developing Atrial Fibrillation in their lifetime. Currently, only 3,000 (0.1%) annually are treated with a procedure that is complex, risky and not widely available. This project will help develop a device that will provide doctors a safer, simpler and lower cost procedure that will serve larger numbers of people suffering from this debilitating condition.